SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6450c8b1193c66f5f6340ecdee94fd1a82b62b0a8d985fcf4ebcfd442f6906b' 
  AND token = 'zkJ+h1SjI595OggYclL8nbQZ+yrj1z8qGigpPYhpVPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}